I noticed on my new boiler that the installer used Vent-Rite #75 main vents. I can find information for Dole and Hoffman, but not Vent-Rite. I think they have been bought out. I wonder if anyone has the pressure spec for this vent? I know for this boiler there should be low pressure (about 3psi) mains. Also when installing main vents should they be located up above the mains on a length of pipe instead of right into the main? I know they close on pressure, but how about temperature?